He was a National League winner of five consecutive Gold Glove Awards for defensive fielding excellence at third base (1964–1968).[5][6] He set or tied NL records by leading the league's third basemen in total chances eight times, in games, putouts and assists seven times each, and in double plays six times;[4] from 1966 to 1974 he held the NL record for assists in a single season. He also set NL records for career assists (4,532), total chances (6,777) and double plays (389) at third base, all of which were eventually broken by Mike Schmidt between 1986 and 1988; his NL total of 2,102 games at third base fell 52 short of Mathews' league record, and he then ranked sixth in NL history in putouts (1,930) and ninth in fielding percentage (.954).

Santo enjoyed his success despite suffering from diabetes, a condition which he carefully concealed for 80% of his career; it eventually necessitated the amputation of the lower half of both his legs.[7] From 1990 until his death he was a member of the Cubs broadcasting team.[7] While Santo initially received little support for induction into the Baseball Hall of Fame, his standing among baseball enthusiasts and sabermetricians gradually increased over time, culminating with his induction to the Hall of Fame through the Golden Era Committee in 2012, two years after his death.[1][8][9]

Santo was signed as a free agent by the Chicago Cubs in 1959, and made his debut on June 26, 1960.[10][11] In 1961 he set a Cubs record with 41 double plays at third base, breaking the previous mark of 33 set by Bernie Friberg in 1923. In 1962 he led the National League in assists for the first time with 332, setting the team record for assists at third base, breaking the mark of 323 set by Randy Jackson in 1951. Santo continued to lead the NL in assists every year through 1968, breaking Ned Williamson's major league record of leading the league six times; Brooks Robinson went on to lead the American League eight times. Mike Schmidt eventually tied Santo's NL mark of seven. In 1963 Santo broke the modern NL record with 374 assists at third base, passing Tommy Leach's 1904 mark of 371. In 1966, he set the all-time league record with 391, the previous record being Billy Shindle's 382 in 1892; his total was 99 higher than that of league runner-up Ken Boyer. Santo broke his own record in 1967 with 393 assists,[12] which remained the NL record until Schmidt posted 404 in 1974. He also finished fourth in the 1967 NL Most Valuable Player Award voting results.[13] Santo's assist totals from 1963 through 1968 were the six highest by an NL third baseman between 1905 and 1973. He also led the NL in putouts every year from 1962 through 1967 and again in 1969, tying the league record shared by Pie Traynor and Willie Jones in leading the league seven times;[14]Tim Wallachlater tied the mark as well.

Santo was deeply saddened by the loss of teammate Ken Hubbs, the Cubs second baseman, killed in a plane crash just prior to the 1964 season. Santo was interviewed by Tom Harmon, narrator of the film A Glimpse of Greatness–The Story of Ken Hubbs, in which Santo paid the highest respects to the young Hubbs.[citation needed]

During the 1969 season, Santo became known for performing a heel click after a game on June 22, 1969, against the Montreal Expos.[12][18] Going into the bottom of the ninth inning, the Expos were leading 6–3. With one out, Paul Popovich hit a single, and moved up to second base after another single by Billy Williams. Although Santo grounded out for the second out, Popovich and Williams each moved up a base. Then future Hall of Famer Ernie Banks singled to bring home Williams and Popovich and bring the Cubs within a run. Rick Bladt substituted as a pinch-runner for Banks. That set it up for Jim Hickman, who hit a two-run walk-off home run to win the game 7–6.[19] When Hickman reached home plate, Santo was so excited that after congratulating him by bear hugging and pounding him on his head, Santo ran down the third base line and jumped three times, clicking his heels on each jump.[7][12]

The next day, Santo walked into managerLeo Durocher's office; Durocher asked him to keep clicking his heels whenever the Cubs won at Wrigley Field to motivate the team. Santo continued this after every home win. The stunt antagonized opponents and served to make the team a target for payback in the final weeks of the season. When the Cubs began their September swoon, which took place shortly after Santo called out rookie teammate Don Young in public after a loss against the Mets in New York, he discontinued the heel click routine suddenly. His final "click" was performed on September 2, the last Cub home victory while still in first place. During and after the epic collapse, Santo never again performed the heel click, as critics decried the routine for its arrogance and overconfidence, which many believe was at the root of the late fade.[citation needed] On the day Santo was enshrined in the Hall of Fame, the Cubs' starting line-up all did the "kick" at the start of the game in tribute.

In 1973, Santo became the first player to invoke the ten-and-five rule under the collective bargaining agreement signed after the 1972 Major League Baseball strike (the rule allows players with 10 years' service, the last five with the same team, to decline any trade).[12] The Cubs had agreed upon a deal to send Santo to the California Angels; the ballclub would have received in return two young pitchers: Andy Hassler, who went on to have a middling career as a reliever/spot starter, and Bruce Heinbechner, a very highly regarded left-handed pitching prospect, who died before beginning of the 1974 season.[20] Santo didn't want to play on the West Coast and vetoed the deal.

The Cubs still wanted to trade Santo, and since his preference was to stay in Chicago, they worked out a deal with the White Sox in December 1973, acquiring catcherSteve Swisher, and three young pitchers: Jim Kremmel, Ken Frailing, and one of Santo's future co-broadcasters, Steve Stone.[11] The White Sox already had a third baseman, Bill Melton, so Santo was relegated mostly to designated hitter duty, which he hated. He wanted to play in the field, but White Sox manager Chuck Tanner wouldn't bench Melton (who had had a couple of 30 home run seasons for them), so he unsuccessfully tried Santo at second base. Finishing 1974 with a .221 batting average and 5 home runs, Santo retired from baseball at the age of 34.[10]

Santo led the league in double plays six times (1961, '64, '66–'68, '71), tying the major league record held by Heinie Groh;[4] Mike Schmidt also later tied this record. He led the National League in total chances every season from 1961 through 1968.[4] He appeared at third base in every Cubs game from April 19, 1964 through May 31, 1966, establishing a league record with 364 consecutive games at the position;[4][12] his 164 games at third base in 1965 remain the major league record.

He won the NL Player of the Month award three times: June 1963 (.384, 6 HR, 22 RBI); July 1964 (.395, 7 HR, 27 RBI); and June 1969 (.400, 6 HR, 34 RBI).

Santo broke Eddie Mathews' NL record of 369 career double plays at third base in 1972, and in 1973 he broke Mathews' league records of 4,284 assists and 6,606 total chances. Schmidt passed Santo's record for double plays in 1986, his record for assists in 1987, and his mark for total chances in 1988. During his 14-season run with the Cubs, Santo hit 337 home runs, then the eighth most by a NL right-handed hitter; his 1,071 career walks with the Cubs remain the team record for a right-handed hitter. He was the first third baseman to hit 300 home runs and win five Gold Gloves, a feat since matched only by Schmidt and Scott Rolen.

Santo became the first player in major league history to wear a batting helmet with protective ear flaps, when in 1966, in the midst of trying to break the Cubs' modern consecutive-game hitting streak record of 27 games (set by Hack Wilson in 1929), Santo was sidelined for nearly two weeks following a pitch thrown by the Mets' Jack Fisher (beaning) that fractured his cheekbone and ended his consecutive playing streak. When he returned (and broke the hitting record with a 28-game streak[12]) he was wearing an improvised ear flap on his batting helmet in order to protect the injury; ear flaps have since become standard equipment on batting helmets.

On September 28, 2003, Santo's jersey No. 10 was retired by the Cubs organization, making him the third player so honored behind his teammates Ernie Banks (#14) and Billy Williams (#26).[21] Other prominent Cubs had worn No. 10 after Santo's retirement, notably Dave Kingman and Leon Durham; the most recent wearer had been interim manager Bruce Kimm, just the previous year. In April 2004, Santo was inducted into the inaugural class of the Washington Interscholastic Activities Association (Washington's high school athletics league) Hall of Fame as a graduate of Seattle's Franklin High School.[22] About a month after Santo's death, Cubs Chairman Tom Ricketts announced that Santo would be honored by the Cubs in the 2011 season. From spring training through the end of the season, the Cubs wore a patch on the sleeve of their jersey with the number 10 on it.

When Santo first became eligible for election to the Baseball Hall of Fame in 1980, he was named on less than four percent of all ballots cast by the Baseball Writers Association of America (BBWAA), resulting in his removal from the ballot in subsequent years; he was one of several players re-added to the ballot in 1985 following widespread complaints about overlooked candidates, with the remainder of their 15 years of eligibility restored even if this extended beyond the usual limit of 20 years after their last season. After receiving 13 percent of the vote in the 1985 election, his vote totals increased in 10 of the next 13 years until he received 43 percent of the vote in his final year on the 1998 ballot, finishing third in the voting behind electee Don Sutton and 2000 inductee Tony Pérez.

Following revamped voting procedures for the Veterans Committee, which had elected players retired for over 20 years to the Hall of Fame, Santo finished third in 2003, tied for first in 2005, and again finished first in voting for the 2007 and 2009 inductions, but fell short of the required number of votes each year.

Santo's next opportunity for admission to the Hall of Fame following a further major change to the voting structure and process announced in 2010, came during the voting in 2011 by the new 16-member Golden Era Committee which considers every three years, ten candidates identified by the Historical Overview Committee from the 1947 to 1972 era.[23]

Although Santo became a widely supported candidate for selection, his initial poor showing in balloting has been attributed to various factors, including a longtime tendency of BBWAA voters to overlook third basemen; at the time Santo retired, only three of the over 120 players elected were third basemen, and only Pie Traynor had been elected by the BBWAA. Also, the fact that Santo's best years occurred in the 1960s, when offensive statistics were relatively lower than in many other eras (due to an enlarged strike zone and raised pitcher's mounds, among other things), has been cited as a factor that led the voters to perhaps overlook him.[24][25] Another possible reason that was suggested was that voters had not focused sufficiently on Santo's high walk totals and defense. These aspects of play are perhaps more valued by sabermetrics — newer methods of evaluating a baseball player's productivity — than they have been by BBWAA voters in the past. For example, Santo's career adjusted on-base plus slugging (OPS+; the sum of a player's on-base percentage and slugging percentage, adjusted for the park and league in which he played, and expressed as a percentage of the league average) would rank him exactly in the middle of the ten major league third basemen who were in the Hall of Fame in 2011.[25][26]

One argument that was raised against Santo's Hall of Fame candidacy is that his batting statistics, over the course of his career, were significantly better at home than on the road. He hit 216 of his 342 home runs at home, and only 126 on the road.[27] His career batting average at home was .296, versus .257 on the road.[27] However, several players elected to the Hall of Fame by the BBWAA, such as Carl Yastrzemski, Wade Boggs, Jim Rice and Kirby Puckett, batted significantly better in their home parks than they did on the road.[28][29][30][31] Hall of Famers with a significant differential between their home numbers and road numbers in terms of home runs include Mel Ott (323 homers at home and 188 on the road), Frank Robinson (321 at home, 265 on the road), Jimmie Foxx (299 at home, 235 on the road) and Hank Greenberg (205 at home, 126 on the road).[32][33][34][35] Others have also commented that two Cub players who were in their prime during Santo's prime years have already been honored by the Hall of Fame (Ferguson Jenkins and Billy Williams), and the Cubs also featured a third Hall of Famer, Ernie Banks, who was arguably past his prime, yet the team never won a pennant. However, the late 1960s Cubs were far from the only team in baseball history with multiple Hall of Famers that did not win a pennant or a World Series.

Even though Santo was disappointed at being bypassed by the Hall of Fame, on the day his jersey number 10 was retired by the Cubs, the ever-optimistic and emotional "old Cub" told the cheering Wrigley Field crowd, "This is my Hall of Fame!"[4][40] During Ryne Sandberg's Hall of Fame acceptance speech in 2005, he echoed his support for Santo's selection, saying, "...for what it's worth, Ron Santo just gained one more vote from the Veterans Committee."[41] On April 19, 2007, the Illinois House of Representatives adopted HB 109 (Cross), urging the Veterans Committee of the Baseball Hall of Fame to elect Ron Santo to the Baseball Hall of Fame. [42]

On December 5, 2011, the 16-member Golden Era Committee that began voting on ten candidates selected by the BBWAA screening committee,[43] was composed of Hank Aaron, Pat Gillick, Al Kaline, Ralph Kiner, Tommy Lasorda, Juan Marichal, Brooks Robinson, Billy Williams, Paul Beeston, Bill DeWitt, Roland Hemond, Gene Michael, Al Rosen, Dick Kaegel, Jack O'Connell, and Dave Van Dyck. They were charged with determining whether Santo would be elected to the National Baseball Hall of Fame's Class of 2012. Williams, Santo's long-time teammate and friend, had made a fresh case for Santo, emphasizing his personal struggle with diabetes during his career, and his post-retirement charitable work to try to find a cure. Santo received 15 of the 16 possible votes and was the only one of the ten Golden Era Ballot candidates to be elected to the Hall of Fame by the Committee's first time voting[1][9][44](no candidates were elected in 2014). Santo's widow Vicky accepted the plaque on Induction Day, and spoke about his love of the Cubs and his devotion to sufferers of diabetes.

In the early years of his playing career, he carefully concealed the fact that he had type 1 diabetes. He feared that if this information were to be known, he would be forced into retirement. Because the methods of regulating diabetes in the 1960s and 1970s were not as advanced as they are today,[9] Santo gauged his blood sugar levels based on his moods.[46] If he felt his blood sugar was low, he would snack on a candy bar in the clubhouse.[46]

As part of the publicity surrounding "Ron Santo Day" at Wrigley Field on August 28, 1971, he revealed his struggle with diabetes. He was diagnosed with this disease at the age of 18, and was given a life expectancy of 25 years. Santo had both his legs amputated below the knee as a result of his diabetes: the right in 2001 and the left in 2002.

In 2004 Santo and his battle against diabetes were the subject of a documentary, This Old Cub. The film was written, co-produced and directed by Santo's son Jeff.[9]

Santo shared a bond in this respect with 2008 Cub rookie Sam Fuld, who also suffers from type 1 diabetes.[47]

Santo endorsed the Juvenile Diabetes Research Foundation's annual Ron Santo Walk to Cure Diabetes in Chicago from 1979 until his death, and raised over $65 million for the Juvenile Diabetes Research Foundation (JDRF). In 2002, Santo was named the Juvenile Diabetes Research Foundation's "Person of the Year".[40] Santo also inspired Bill Holden to walk 2,100 miles from Arizona to Chicago, to raise $250,000 for diabetes research.

On Wednesday, August 10, 2011, Ron Santo was memorialized and "immortalized" at Wrigley Field with the presentation of a statue in his likeness. The statue is a portrayal of a young Ron Santo playing defense at third base, leaning to his right while throwing a ball.